The present invention relates to apparatus for forming a wrapped thread from a fiber supply, the process being commonly referred to as wrap spinning, and more particularly to such apparatus in which the speeds of drafting rolls feeding a binder spindle are electronically controlled to maintain respective speeds which are individually preselectable proportions of the speed of the spindle.
In the wrap spinning of yarn, fibers are drawn or "drafted" from a supply of the fibrous material by a succession of drafting rolls. The successive rolls are run at increasing speed so as to draw out the fibers to an appropriate weight. From the drafting rolls the fibers are fed through a spindle which contains a supply of a filament binder. The binder spindle, operating at a relatively high rotational speed, wraps the binder filament around the fiber sliver thereby completing the yarn. As is well understood by those skilled in the art, the characteristics of the finished yarn are affected by the relative speeds of the successive drafting rolls and also by the relative speed of the binder spindle.
In conventional wrap spinning apparatus, it is common for a large number of wrap spinning stations to be driven from a common motive source, usually a large, variable speed electric motor. The speed differential between successive drafting rolls is established either by gearing between the shafts driving the successive roll stages or by providing different motors which are manually adjusted to appropriate speeds. All binder spindles are typically driven through a tangential belt drive from a variable speed motor, speed of such motor being operator selectable.
In the event of a malfunction at one wrap spinning station, i.e., due to a yarn break or the need to refill a binder spindle, all of the commonly powered stations must be stopped to service the malfunctioning station. Further, the restarting procedure is difficult to achieve without inducing further breaks or a deviation in the characteristics of the yarn since it is difficult to bring all speeds up to the desired final operating speeds while maintaining the desired speed relationships.
Among the several objects of the present invention may be noted the provision of apparatus for forming a wrap thread from fibers in which the speeds of successive drafting rolls are electronically controlled through respective roll motors to operate at respective speeds which are individually preselectable proportions of the speed of the binder spindle; the provision of such apparatus in which the speed of the spindle is electronically controlled to a speed corresponding to the operating frequency of a variable oscillator; the provision of such apparatus which facilitates the independent operation of a plurality of wrap spinning stations; the provision of such apparatus which facilitates the restarting of a wrap spinning station following the break of a thread or the restocking of supply materials; the provision of such apparatus which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.